Display devices are capable of restituting information data to a user in a visual manner, by using pixels to create an image on a screen. In order to increase the visual comfort of the user, there is a trend that screens are made bigger and bigger and therefore a higher image quality is required. Moreover, in order to enhance the display capabilities and have more information available at the same time, in some applications several screens of various size and shapes are used for displaying information on one and the same display board, for instance. Also, in order to save space, screens may be partially occluded by plastic covers. Therefore there may be parts of a screen that are hidden so that it is not seen by the user.
Most display devices have a rectangular screen since the rectangular shape is particularly convenient for the manufacture and control of the screen. It results thereby that the current state of the art of data processing for displaying images is tied to the rectangular shape of conventional screens. For instance, frame buffers, which are data memory areas wherein pixel values associated with respective images are stored before being processed in order for the images to be displayed in sequence, may be designed as data structures wherein data is addressable by rows and columns. Indeed, such data structure conveniently suits a rectangular display screen for which pixels of an image are also arranged as a matrix of N rows and M columns, where N and M are integral numbers.
Display systems further include a data processing unit for fetching pixel values from frame buffers of the data memory, and converting the pixel values into electrical signals suitable for controlling the display of the successive images on the screen. The pixel values of an image are sequentially displayed within a predetermined period of time tied to the refresh rate of the screen, which may be 50 Hz or 60 Hz, for instance, for standard video applications. However, the updating rate for pixel values in the frame buffers is limited as a result of technological and/or functional limitations of the data memory. When access to the data memory is too slow or is constrained by existing priorities to serve other host units, it may be impossible to fill the buffers at a rate required by the data processing unit, for instance at a rate of 50 Hz or 60 Hz. Given that the data processing unit is configured to update the image displayed on the screen at a steady frame rate which is independent of the latency associated with accesses to the data memory, the data processing unit may continue the processing whereas one or more frame buffers lack updated pixel values. Therefore, the data processing unit may fetch non-updated pixels values from the frame buffers, which may result in a failure to display the intended images properly. Going forward, if the latency gets too high, the pixel values are not available and the data processing unit may send arbitrary values to the screen (because the old pixel values are no longer available).
Hence, the image seen by the user on the screen may have a degraded quality due to bandwidth issues with respect to the access to frame buffers in data memory.